Milo g



M. G. KELLOGG.

MULTIPLE SWITGHBOARD.

(No Model.)

Patented Oct. 26

NITED STATES FFICE.

PATENT MILO G. KELLOGG, OF CHICAGO, ILLINOIS, ASSIGNOR TO THE KELLOGGSIVITCIIIEOARD AND SUPPLY COMPANY, OF SAME PLACE.

M ULTIPLE SWITCHBOARD.

SPECIFICATION forming part of Letters Patent No. 592,408, dated October26, 1897.

Application filed August 31,1891. Serial No. 404,336. (No model.)

T0 to whom it may concern.-

Be it known that I, MILO G. KELLOGG, of Chicago, in the county of Cookand State of Illinois, have invented certain new and useful Improvementsin Multiple Switchboards for T elephone-Exchanges, of which thefollowlng is a full, clear, concise, and exact description, referencebeing had to the accompanying drawings, forming a part of thisspecification.

My invention relates especially to a metallie circuit telephone exchangesystem in which inductioircoil translators or converters, one for eachline at the central office, are employed to translate thetelephone-currents from one circuit or line to another circuit or line.

It consists of a system for calling, switching, testing, andclearing-out signals for such an exchange which I shall describe andclaim in detail.

In the accompanying drawings, illustrating my invention, Figure 1represents sectional views of two switchboards with the centralofficeswitches and apparatus for two lines of the exchange and the connectingand answering apparatus at each board for answering calls, connectingthe translators of the two lines, testing to see whether the lines arein use, and receiving clearing-out signals for a connection which may bemade. Fig. 2 shows in diagram a subscribers-station apparatus to be usedin the exchange system.

In Fig. 1, A A are two switchboards. Other boards may be added and usedas required for the size of the exchange. Each board has a metal socketor switch contact-piece for each line. These sockets or contact -piecesare marked jj and are each adapted to receive the switch-plugs at theboards, and thereby form contact with the contact-piece of the plug andalso have the test-plu g contactpieces applied to them for testing. I Iare induction-coil translators, one for each line. i tareinduction-coils, and T T are test-plugs, one of each for each operator.One coil of each of these induction-coils is in circuit with thetelephone of the operator. The testplug T is connected to a flexibleconductor and is adapted to be brought for testing into contact witheach contact-piece j at its board and is connected through the othercoil of the ind notion-coil with the metal conductor hereinaftermentioned. w w are two annunclators, one for each line.

At each board there is a pair of plugs, (marked D D,) a test-battery forthe pair of plugs, (marked B,) a clearing-out ann unciator for the pairof plugs, (marked 11,) an operators telephone, (marked 1,) a switch forthe pair of plugs, (marked Y,) and a callinggenerator, (marked B.)

The switch Y has a lever and three contact-bolts on which the lever mayalternately be placed. The plugs of a pair are connected together byflexible conductors, and in the circuit between them is theirtest-battery B. Each plug is adapted to be placed in connection witheach metal socket j at its board. The lever of the switch is connectedto the circuit which connects the two plugs, preferably so that thebattery B is in circuit between the lever and the plug D. One side ofthe telephone, one side of the calling-generator, and one side of theclearing out annunciator are connected with the three contact-bolts,respectively, of'the switch Y. The other sides of thetelephone,calling-generator, and clearing-out annunciator are connectedtogether by metal conductor and are connected by metal conductor withthe same side of the various other instruments of the same kind in theexchange. One side of one of the coils of eachtranslator is connected bymetal conductors with the same sides of these instruments. Only one pairof plugs, with their special apparatus, is shown at each board. Onetelephone answers for each operator and one calling generator may beused for the whole exchange. Other pairs of plugs, with their specialapparatus, may be added for each operator as she may need, and theirconnection to the other apparatus is substantially the same as has beendescribed and is shown and as will be apparent to those skilled in theart.

The other side of each translator-coil mentioned above is connected tothe metal sockets j j of the line to which the translator belongs. heother coil of each translator is connected into circuit with its line.From the center of the last-mentioned coil of each line a branch wirepasses to ground through the grounded at the central office.

.tions which will hereinafter be described.

When the key 5is pressed, the line-circuit is Otherwise the line-circuitis not grounded there. When the generatorlis operated, itis in themetallic circuit of the line. WVhen the telephone is on the switch,thesignal-bell is in the direct circuitnof the line, andwhen thetelephoneis off'the switch it is itself in the directcircuit of the line.

The operation of the system i'sasfollows: When a subscriber wishes tomake a call, he presses. on his key 5 and while doing so operates hiscalling-generator. A callingcurrent then passes in a circuit from theground at his station through that side or branch of the line in whichthe generator is to ground at the central office, through theline-annunciator,andoperates the annunciator. Part of the currentgenerated will pass throughthe complete metallic circuit of the line,but enough-will pass through the groundcircuit traced above to operatethe annuncia: tor. hen the operator to whom. the annunciator is assignedobserves the call, she places one of her switch-plugs D into the metalsocket of the line at her board and moves the lever of the switch Ybelonging to theplugso that her telephone is in connection with it. Acomplete metallic circuit is thus established in which is. included theoperators telephone, the test-battery B',,and the local coil of thetranslator of the line. The subscriber having takenhis telephone fromits 'switch,the telephone is included in a metallic circuit with theline and the other coil ofthe translator. The subscriber and operatormay then converse and. the subscriber give. his call. The operator thentests the line wanted, as will be described,.and if. it tests not in useplacesthe mate to the plug (marked D7) into the metal socket of the linewanted, The local coil of the translator of the line wanted is therebyconnected in a.

metallic circuit withthe local coil of the calling line, and thiscircuit has the test-battery Bofthe pair of plugs in it andis bridged orcross-connected by the operators telephone. of'the switch Y so that itis in connection with the calling generator and the generator isinabridge-circuit of the metallic circuit containing the two coils, andthe generator being operated current goes throughboth coils andiinducedcurrent is generated in .the metallic circuit of both. lines, thesubscriber wan ted'will therefore be rung.

The operator then moves the lever. telephone.

phone and secondary of the induction-coil when a test is made is,,say,from plug D in the contact-piece of the calling-line, thence through thetranslator-coil of the line to the common wire which unites thetranslatorcoils, vthence through the telephone and secondary of theinduction-coil 2' to the lever of fthe switch Y, and thence through theflexible The bell of.

The operator then moves the lever of the switch; Y so that it is inconnection with the clearing-out annunciator, and the annunciator isthereby connected in a bridge or crossconnection of the metallic circuitwhich contains the two translator-coils. The subscribers can thenconverse, the telephone-cur- .rents being translated from onemetallic-circuit line to the metallic circuit which contains the twolocal coils and from said circuit to the other metallic-circuit line.

When a subscriber wishes to send a clearing-outsignal, he operates hiscalling-genera- 'tor without pressing on his key 5. is thereby generatedin his metallic-circuit A current line and an induced current isgenerated in the local coil of the line which will operate theclearing-out annunciator which is in circuit with such coil (being in a.cross-connecting circuitto the circuit of the two local coils of thelines). and between the two coils.

When the contacts of two lines are connected together and the circuit oftheir induction-coils is bridged by aclearing-out anplacesher test-plugT on the contact-piece j at her board of the line to be tested. If,then, the line has a switch-plug in one of its contact-piecesj atanother board,a complete circuit is established, which contains one coilof the induction-coil dot the operator making the test and the batteryB, which is in circuit with the switch-plug which isin said contactpiece j. This circuit may-be traced as follows: from the metalconductor heretofore mentioned through the coil of the induction-coil tothe test-plug T, thence to the contact-piece j, where the test is made,thence to the contact-piece j, in which the switch-plug is i11- serted,and thence through the batteryin circuit with the plug and a local coil1., connected with it, to the metal conductor. A current will thereforepass through the coil of the induction-coil which will cause an inducedcurrent in the other coil of the induc-. tion-coil and make a click inthe operators The closed circuit of the telecord to D. If there is noplug in a contactpiece j of the line, no such complete circuit isestablished which contains the coil of the i11- duction-coil t' of thetesting apparatus and a battery and no click will be made in hertelephone. She can therefore determine on testing whether or not theline is in use.

The connections of the local coils of the translators and of theoperators apparatus to the same are all metallic and without groundconnection or circuit, and therefore when two coils are connectedtogether for purposes of conversation their circuit is not subject tointerference from earth currents or connections. These advantages wouldto a certain extent be obtained should themetallie-circuit connection Ihave described be purposely or accidentally connected with the ground ata certain point.

The induction-coils Q1 2', with their telephones 25 t, may be consideredas test receiving instruments. Other forms of test receiving instrumentsmay be used.

It will be observed that when two of the local coils of translators areleft connected into a complete metallic circuit for conversation betweentwo subscribers the circuit is bridged between the coils by aclearing-out annunciator. This annunciator should preferably be of sucha construction as to offer considerable retardation to the passage oftelephone-currents. \Vith such a construction no great amount of thetelephone-current will be diverted from the complete nietallic circuitof the two coils and the conversation will not be materially reduced. Iffor any reason the clearing-out annunciator should not be retained andstill the bridge connection be retained, I prefer to place in the bridgeconnection some other form of retardation apparatus totelephone-currents.

I claim as my inVention- 1. In a telephone-exchange system, multipleswitchboards, metallic-circuit lines and translators at the centraloffice for said lines, one translator for each line, one coil of whichis in the circuit of the line, in combination with switch-contacts, oneforeach line on each board, the contacts of the line being connectedtogether and connected to one side of the other coil of the translator,the other side of said coil being connected by metallic connection withthe same side of the other like coils of the translators, switchapparatus at each board to connect together any two of saidswitch-contacts at the board, a clearing-out annunciator bridged acrossthe circuit of the coils of two lines thus united and a callinggeneratorat either of the subscribers stations operated in the circuit of hisline to send a clearing-out signal, substantially as set forth.

2. In a telephone-exchange system,a switchboard, metallic-circuit linesand translators at the central office for said lines, one translator foreach line, one coil of which is in the circuit of the line, incombination with switchcontacts on said board, one for each line, to

which one side of the other coil of the linetranslator is connected, ametallic connection between the other sides of said other coils of thetranslators, switch apparatus to connect together any two of saidswitch-contacts at the board, a clearing out annunciator bridged acrossthe circuit of the coils of two lines thus united and acalling-generator at either of the subscribers stations operated in thecircuit of his line to send a clearing-out signal, substantially as setforth.

8. In a telephone-exchange syste1n,a switchboard, 1netallic-circuitlines and translators at the central office for said lines, onetranslator for each line, one coil of which is in the circuit of theline, in combination with switchcontacts on said board, one for eachline, to which one side of the other coil of the linetranslator isconnected, an ungrounded I110- tallic connection between the other sideof said last-mentioned coil and the same side of the same coils of theother translators, switching apparatus to connect together any two ofsaid switch-contacts, a clearing-out annunciator bridged across thecircuit of the coils of two lines thus united and a calling-generator ateither of the subscribers stations operated in the circuit of his lineto send a clearing-out signal, substantially as set forth.

4. In a telephone-exchange syste1n,a switchboard, telephone-lines andtranslators at the central ofliee for said lines, one translator foreach line, one coil of which is in the circuit of'the line, incombination With switch-com tacts, one for each line on the board,connected to the one side of the other coil of the translator of theline, metallic connections between the other side of said last-mentionedcoil and the same side of the same coil of each of the othertranslators, switching apparatus to connect together any two of saidswitchcontacts a clearing-out annunciator bridged across the circuit ofthe coils of two lines thus united and a calling-generator at either ofthe subscribers stations operated in the circuit of his line to send aclearing-out signal, substantially as set forth.

5. In a telephone-exchange system,a switchboard, telephone-lines andtranslators at the central oflice for said lines, one translator foreach line, one coil of which is in the circuit of the line and one sideof the other coil of which is in a completely metallic connection withthe same side of the same coil of each of the other translators, incombination with switch apparatus to connect together the other sides ofany two of such coils of the translators a clearing-out annunciatorbridged across the circuit of the coils of two lines thus united, abattery in circuit with said clearing-out annunciator, and acalling-generator operated at either of the subscribers stations in thecircuit of his line to send a clearing-out signal.

6. In a telephone-exchange system,aswitchboard, telephone-lines andtranslators at the central office for said lines, one translator foreach line, one coil of which is in the circuit of the line and one sideof the other coil of which is in ungrounded completely metallicconnection with the same side of the same coil of each of the othertranslators, in combination with switch apparatus to connect togetherthe othersides of any two of the lastmentioned coils of the translators,a clearingout annunciator bridged across the circuit of the coils of twolines thus united, a battery in circuit with said clearing-outannunciator,

and a calling-generator operated at either of the subscribers stationsinthe circuit of his line to send a clearingout signal substantially asset forth.

7 In a telephone-exchange system, multiple switchboards,metallic-circuit lines and translators at the central office for saidlines, one translator for each line, one coil of which is in the circuitof the line, in combination with switch-contacts, one for each line oneach board, the switch-contacts of a line being connected together andto one side of the other coil of the translator of the line and theother side of said coilbeing connected through metallic conductor to thesame side of the same coil of each of the other translators, pairs ofplugs at each board, the plugs of each pair being connected by aflexible conducting-circuit and each plug adapted to form connectionwith each of said switch-contacts at its board, a battery in circuitbetween the plugs of each pair, a clearing-out annunciator bridgedacross the circuit of the coils of two lines united by the plugs of apair of plugs and a calling-generator operated at either of thesubscribers stations in the circuit of his line to operate theclearing-out annunciator substantially as set forth.

8. In a telephone-exchange system, multiple switchboards,metallic-circuit lines and translators at the central oifice for saidlines, one translator for each line, one coil of which is in the circuitof the line, in combination with switch-contacts, one on each board foreach line, said contacts of each line being connected together bymetallic conductor and to one side of the other coil of theline-translator and the other sides of the same coils being metallicallyconnected together, switching apparatus to connect together any two ofsaid switch-contacts on any board, a battery between them when thusconnected, a clearingout annunciator bridged across the circuit of thecoils of two lines thus connected and test receiving instruments, one ateach board, each connected metallically on one side to thelast-mentioned side of the last-mentioned coils of the translators andon the other side to a plug or device adapted to be brought for testinginto connection with each of said switch-contacts at its board,substantially as set forth.

9. In a telephone-exchange system, multiple switchboards,telephone-lines and translators at the central office for said lines,one translator for each line, one coil of which is in the circuit of theline, in combination with switch-contacts, one on each board for eachline, said contacts of the line being connected metallically to one sideof the other coil of the line, the other side of the coil beingconnected metallically with the same side of each the same coils of theother translators, switching apparatus to connecttogether any two ofsaid switch-contacts on any board,

a battery between them when thus connected, a clearing-out annunciatorbridged across the circuit of the coils of two lines thus connected andtest receiving instruments, one at each board each metallicallyconnected on one side to the last-mentioned side of the lastmentionedcoils of the translators and on the other side to a plug or deviceadapted to be brought for testing into connection with each of saidswitch-contacts at its board.

N 10. In a telephone-exchange system, metallic-circuit lines andtranslators for said lines, one translator for each line one coil ofwhich is in the circuit of the line, in combination with theline-annunciator of each line grounded on one side and connected on theother side to the center of said coil of the line, a calling-generatorin the circuit of the line at the subscribers station, switchingapparatus at the subscribers station to at will ground the line-circuitthere, a switching apparatus to at will connect together the two othercoils of any two translators, and a clearing-out annunciator bridgedacross the circuit thus established through said coils and from betweensaid coils, substantially as set forth.

In testimony whereof I have hereunto subscribed my name.

MILO G. KELLOGG.

Witnesses:

CALVIN DE WOLF, FRANCES D. KELLOGG.

